Pole position self-sensing of surface-mounted PMSM using high-frequency injection

High-frequency (HF) injection based pole position self-sensing technology is promising in ture sensorless drives for permanent magnet synchronous motors (PMSMs), in virtue of its robustness independent of operating point. Two prevailing methods in academic and industrial world, which respectively adopt HF rotating and oscillating voltage excitation, are the focus of the paper. Differences between them in the generation, acquisition and processing of the signals used for estimating the pole position are described in detail. Specifically the influence of dead-time effect on HF voltage injection is analyzed, comparing these two types of excitation. In experimental research on a surface-mounted PMSM, the effectiveness and practicality of the approach is verified by sensorless estimation performance under low and zero speeds. Further, main error sources, including multi-saliency effect of tested motor and low sampling rate in digital implementation, are indicated.